Working with available materials for solar cooker construction

- Stephen Harrigan, Solar Clutch, 2012

“Available material” is a major factor in making solar cookers practical around the world.
Take the CooKit as an example: We assume that cardboard is readily available everywhere and cheap to obtain. However most regions of the world where they most need solar cooking you will not find cheap cardboard. You have to buy the cardboard box from a local merchant. And most likely it is torn and has holes in it that you have to patch with tape (which then you have to buy a roll of tape.) Then you have to find aluminum foil….again not easy to locate except in a “Western” supermarket. Price goes up accordingly. Glue is usually available but you have to get a whole tin of it…maybe more than you need.
You will also have to buy some razor knives to cut out the cardboard and foil.
Your cardboard CooKit still has to be reinforced at the joints and seams and finger tips. At best it will last 6 months, and then you do this all over again.
Even though at Solar Clutch we love our Poly-Furnace …. alas the material, however good it is, might as well be from the moon as most places haven’t a clue what polypropylene fluteboard is or Mylar.
Is there another alternative material? “Cool Roofing” material.
Everywhere in Africa and most of the Third World you will find roofing pan that is galvanized or zinc coated.
In the past the galvanized coating has been dull and oxidized over time. But with of the improvements in zinc coating you will find zinc pan that is highly reflective to the level of aluminum. In the effort to reflect the heat in the tropics the zinc roofs are now looking like mirrors dotting the country side. I noted this April 2012 in Ethiopia.
So I went to the market in Addis Ababa and purchased some flat rolled zinc tin of medium grade thickness. With the help of my Ethiopian crew we made a CooKit. We had to cut it with tin snips and bend the seams with a wood board for a straight edge. The “fingers” we bent over as “dog ears” too keep them locked in. We dulled the sharp edges by rubbing stones against them. The cookit won’t fold up in a little packet but who cares? It is washable and can be left outside or inside. The cost was just about $6 which is about the same cost of buying material for a cardboard and aluminum foil cooker!
I took it to the Afar region of Ethiopia and tested it against our Poly-Furnace cookers. It did its job just fine and although was not as bright as the Mylar, the practicality and availability of material make it much more indigenous option and reproducible by the average guy and definitely will outlast many cardboard cookers.

News and recent developments

January 2013: Solar Clutch finds that a local roofing material makes a good reflector - Stephen and Sheila Harrigan of Solar Clutch, report from Addis Ababa, Ethiopia, where they promote solar cooking, that common solar panel cooker construction materials have always been difficult to obatin. The widely used CooKit has traditionally been made from cardboard, though recent versions are being made from fluteboard, such as the Poly Furnace CooKit variation. These updated cookers last far longer than the cardboard versions, which are considered to be successful if they last six months. For them however, the major problem with providing inexpensive yet durable cookers is the availability of construction materials. Cardboard is scarce, and when it is commercially available, the quality if often poor, or the product arrives torn. Tinfoil and glue can also be difficult to find. Stephen began looking more closely at what was available locally, and hit upon a product referred to as 'cool roofing'. Cool roofing is a zinc galvanized metal material, which is fairly reflective. Besides shedding water, it is also intended to reflect the hot sun from the roofs of local homes. And because of its availability, the material cost for cookers is competitive with cardboard. A CooKit can be constructed for about $6USD worth of the metal roofing. It can be cut with tin snips, and bends are made by folding the metal around a straight board. The metal CooKit has performed well, if not quite as well as the mylar covered fluteboard version, and its weight would help in windy conditions. Because the material is easily available, and can be made with existing worker skills, local manufacturing of solar cookers offers the possibility for a community business enterprise. Disadvantages include the inability to fold the cooker for storage, and transporting completed cookers will take considerable space and will be relatively heavy. The cooker edges need to be dulled or protected, as the cut metal edge is quite sharp. As solar cookers are more widely promoted and accepted, the durability of inexpensive solar cookers becomes a significant issue to be addressed. The question raised will be, is it better to offer a cooker that can be made locally, or find a way to finance the availability of cookers that are made at a more sophisticated facility, losing the empowering aspect of neighborhood manufacturing?

April 2010:Stephen Harrigan runs a U.S.-based nonprofit organization called Solar Clutch that designs and produces solar cookers for distribution to impoverished parts of the world. His cookers include a corrugated plastic solar box cooker called the Sun Scoop and a panel-type solar cooker made from woven baskets and modified clay water pots common in Sudan, called the Borma. Through Solar Clutch, Harrigan also offers consultation and training services to organizations wishing to set up solar cooker programs. In 2006, Harrigan helped the Darfur Peace and Development Organization (DPDO) begin a solar cooker training program for women displaced due to persistent conflict in Darfur. After much research and experimentation, he prepared a solar cooking training model for DPDO. Harrigan selected Solar Cookers International’s cardboard and foil solar CooKit as the primary solar cooker to be used due to its low cost and simplicity. Though the solar cookers are being made locally in Sudan, DPDO has also imported several hundred more durable corrugated plastic versions made by volunteers in the United States. Volunteers in Fort Wayne, Indiana (USA) are making corrugated plastic solar cookers for displaced families in Darfur, complete with uplifting personal messages written on the backs (photo: Solar Clutch) From the beginning, Harrigan believed that DPDO’s infrastructure and ongoing work in internally displaced persons (IDP) camps would be useful in promoting solar cooking. Solar cookers make a lot of sense in these camps because traditional cooking fuels, especially firewood, are in short supply, and the women that forage outside the camps for firewood must not only walk ever greater distances to find firewood, but also risk their personal safety. DPDO reports having trained 321 IDPs to solar cook from 2006 through mid-2009. Workshops have taken place in a number of camps and towns, including: Kalma and Sakali IDP camps in South Darfur, El Fasher town and Kassab IDP camp in North Darfur, and Omdurman and Haj Yousif towns in Khartoum. Women spend less time and energy foraging for firewood outside of IDP camps when they use solar CooKits (photo: DPDO) According to DPDO’s Web site, “workshop participants quickly recognized the time- and money-saving benefits of the cookers, and learned to prepare all of the traditional Sudanese foods. [They] … continue to experiment with recipes, develop cooking-time charts, and conduct training workshops within their communities. DPDO subsidizes training workshops and provides supplies and training expertise, manuals, and follow-up assessment of use.” Future trainings have been scheduled for DPDO women’s centers in Kassab and Abu-Shouk camps, the latter of which was visited by U.S. Special Envoy to Sudan Scott Gration in September 2009. Many of the women at the center had previously been trained and were solar cooking when Gration visited. DPDO reports that Gration “was impressed with [the women’s] efforts and tasted rice that had been cooked with a solar cooker.”

January 2009: In EthiopiaSteve Harrigan made solar cookers with the Ethiopian and Somali people at the Agape Reading Center. The Somali people are already refugees in Ethiopia and in great financial need. Solar cooking is a free source of energy to that allows them to cook without having to use firewood. An Ethiopian couple also was excited to learn how to make solar cookers because they run an orphanage near the Somali boarder and have 30 little mouths to feed 3 times a day! We made cookers from the wheel chair boxes that had been donated to the handicap people of Ethiopia. A double use of the resources God has put at our disposal. If you would like to help provide solar cookers for this orphanage please contact us.